The present invention relates to an air feeding device for an endoscope to feed air into body cavity.
Conventionally, an air feeding device for an endoscope has been known. The air feeding device has an air compressor which compresses the air, and by opening/closing a valve, the air is fed to the human cavity through a tube such as a forceps channel of an endoscope. In such an air feeding device, in order to control the pressure of the air fed therefrom, a pressure control valve is provided. The pressure control valve varies the cross sectional area of a path where the air flows to vary the pressure of the discharged air.
In the air feeding device, the pressure control valve only lowers the pressure of the discharged air. Therefore, in order to control the pressure over a relatively wide range, a large compressor, which is capable of feeding the air at a relatively high pressure, should be provided. Generally, such a compressor should be driven all the time, which generates continuous noise when the endoscope is used for operation. Further, in such a conventional air feeding device, due to a structure of the pressure control valve, it is impossible to feed the air so as to strike an object at a very small pressure, and thus, it is impossible to control the air pressure accurately within a wide range between a very low pressure and a very high pressure.
There has been known a method for detecting hardness of a foreign body in the human cavity by applying air. There has also been known a method for diagnosing organs inside the human cavity by applying air intermittently. In order to use the air feeding device for such diagnosing system, the air feeding device is required to be able to generate a stable and continuous air flow or intermittent air flow, at a relatively low pressure.